Electric circuits



ELECTRIC CIRCUITS Filed July 15, 1919 Patented Dec. 16, 1924.

UNITED STATES.

.PATENT oFF-ier..

EDWARD 0. SCRIVEN, OF NEW YORK, N. Y., ASSIGNQR T WESTERN ELECTRIC COM- PANY,.INCORPQRA TED, OF NEW YORK, N. Y., A. CQRPORATION 0F NEW YORK."

Application filed .Tuly 16,

To all iL-kom, z'tmiy concern.'

Be itknown tliat l, EDWARD O. SCRIVEN,

a eitizeiifof` the- United States, residing at New York, county of New York, Stateof New '.York7 have invented certain new and useful Improvements in Electric Gircuits,

fof which the following is a full, clear, concise, and exact description.

This invention relates to electric circuits and more particularly it relates to repeater circuits wherein filters are employed to eliminate undesired frequencies.

As is well known in the art, undesirable frequencies in 'a .signaling system may be eliminated by inserting electric filters therein composedrof inditctance and capacity of such values as to allow only the desired frequency range.. to pass therethrough. Thus if it .is desired to eliminatev4 all frequencies Iv above a. certain value, while transmitting all shunt capacity of such valuesas may be4 determined by reference tov the Campbell Patent .No.v1,227,l14 ofeMay22, 1917.

It has been found, however, in the use Aof such a 'filterthat its attenuation and its impedance .characteristics Within its transmission" .nge vary somewhat with the freuency. Thisvariation in some cases is un- Y esirable particularly in repeater circuits l wherein a filter of only a few-sepit'ions is em- .ployed and whereinv any distortion duc to 'the unequal attenuation of therfilter is amplified'thereby increasing the distortion still further.'

variation of the attenuation and the impedance vcliaraeteristics of', thefiltcr with l'frequency is avoided by terminating the 'filter in a special network so constructed. as hereinafter described, as to correct the distorting tendencies of the filter.

This correcting net-work preferably cong sists of a resistance inscries with a resonant y circuit comprising inductance and capacity. 1f we represent-the inductance and ca acity .Qfoiie full, section ofthefilter by the c. arac- 1919. seriai No. 311,166.- T

the value ofthe capacity-s'ihould.A be 135 Co 'andthe inductance. 1%' La. It is also preferable that this network be 'connected to a section of the filter that hasonly 36 the capacity-of a full section of the ifilter. The v filter 5 terminatin`g`iii""such' a1 net-work as above described transmits current within its transmission range with 'substantially equal attenuation' regardless of the frequency. When the correcting network has thevalues above defined, its impedance is approximately the' saine as the impedance of the remainder of a lter of infinite length of the type associated with the net-work.

For; a better understanding of this invention, reference is made to the following detailed description taken in connection with the accompanying. drawing which`illustrates the preferred' circuit arrangement of this invention.

Referring to the drawing, interposed between the loaded line '3 and, the amplifier 4, 1s afilter comprising inductances 5 to 12 inclusive and condensers 13 to 1G inclusive. This filter terminates in a net-work composed of a winding 20 of transformer 21 and the resonant circuits consisting of inductancc and capacity 23, and inductaiicc 24 and capacity 25 respectively. The value of capacity 16 in the last section of the filter 85 l should be only approximately' 15% -of the In accoriflanccl with this invention. this capacity of condenser 15whicli represents the total capacity of Ia section of the filter. CondensersQti and which iiijiincluded in the net-workshoiild each bc equal to twice 9" the value, 1&5 Co noted abovcfor-the capacity lof the' correcting net-.work` since-the twin',- .1'

' eoudeuscrs are connected in series and flieiie--"" foreihave :ineffective capacity of shoud 'be "e "ual xto the value 'noted above f for inliictances' of the correcting net,-l work that, is, each should; be 2% of the sunligof inductan'ces 9 and 10 which sum represents the total induct'ance of one full section of the filter. Two resonant circuits are employed in the preferred circuit arrangement in order to preserve the symmetry of the two sides of the line. It',4 desired, however, the inductanceand capacity of this net-work may be inserted in one' resonant circuit instead of being divided-between two resonant circuits.

Thus inductance 24 andcapacity 25 may be -omitted, in which case the value of capacity 3 would be halved and inductance 22 would be doubled. Winding of transformer 21 should` be so designed that its impedance '15 represents a resistanceofa value equal to n 'y l v the'example'ofthe values this cor- 20 recting net-work may have, it may be stated f that in a particular case where the filter was designed to eliminate frequeneiesabove 2000 cycles per second and the inductance persection of the, filter was 0.138 'henrys and the capacity per section was 0.149 microfarads, condensers 23 -and 25 of the network had a capacity of 0.158 microfarads, inductances 22 and 24 each-had a value of 0.0207 lienrysand the effective resistance of winding 2O .was l960 ohms.

`With the capacity, inductance and resistanceof the correcting net-work adj usted as above described, the combination of the l filter andthenet-work will transmit with substantially' equal attenuation to amplifier 4: all currents. from lineV 3 offrequencies within thetransmission range of tlu. filter. Also the impedance characteristics of the filter, as measured from line i), will be substantially` independent of the frequency within the transmission range. It' desired.

the amplified signals in the output of amplifier 4 may befurther `amplified by a second amplifier 3 0 before .being impressed upon the terminals of the outgoing line 3l.

It is to bennderstood that this invention is not limited to the particular circuit ar' rangement above described, but that itv may be variously modified without departing in anywise from. the` spirit of this invention,

as defined in the appended claims.

What is claimed is: l 1. In an electric system, means for simulatin the impedance of a filter of infinite -lengt said means comprising av lter'of finite lengthand a network simulating the impedance of the'remainder of said'filter of infinite length fora wide range of the frequencies freely transmitted by said filter.

: 2. In anelectricsystem, a filter comprising aeplurality of vsimilar sections, each section containing. inductance andI capacity, one of saidy sectionsvha-ving an. electrical I Vcharacteristic avalue 186 the value of said characteristic in another of-said sec'- 05 tions, and a network comprising inductancc, capacity land resistance connected to said firstmentioned section, the elements of said network having values dependent upon the .values of the series and shunt elementsof a section of the filter for equalizing the trans-` vmission of a band'of frequencies. l

` ing an inductance, a separate resistance eft0 I actively in series with said inductance, and capacity in shunt witlrsaid inductance.

4. In an electric system, a filter compris-l ing a plurality of similar sections, one 'of said sectionshaving an electrical charac-T teristic of a value a fractional part'of the. value of saidcharacteristic in another of said'scctions, and a network connected to said first mentioned section, the elements of said network being so proportioned with 9,02

respect to. the filter that the impedance Aof l lthe filter over substantially the entire range slstance.

ceiving terminals therefor and means for preventing undesired4 frequencies from being impressed on said terminals while offering substantially equal attenuation forvall frequencies within a given range, said means loo comprising a wave filter of a plurality of similar sections and a terminating network connected to an end Ysection of said filter havinpr an electrical value onlya fractional part of the corresponding value in another section of said filter, said network being,Y so proportioned with respect .to said filter that the attenuation of said filterfover a given range of free transmission is made substantially constant. A

6. In' an electric system, a line, receiving "terminals therefor, and means for preventing undesiredr frequencies 'fromvbelngimpressed on saidterminals -while offering substantially equal attenuation for all frelli,

quencies within a given range, said means Y, having `an lmpedance simulating the impedance of a wave filter of infinite length-for' a wide range of the frequencies freely trans# j mittedby vsaid means, and comprising avfil 120 ter ofA finite length and a network simulating the impedance of the remainder 'of said filter -of innite length.l

7. In combi11ati )n, any electric wave filter of a plurality of similar sections each comprising a shunt capacity anda network connected thereto 4formaintaining the attenua` tion of all frequencies within the tron .f transmissionl will appear to be pure re- 5. In a transmission circuit, a line, lre- 95 being connected toa section inrluctanee,- said inductance, capacity andA range substantially constant, said 'network of said filter having a shunt capacity approximately equal to eight-tenths the shunt capacity in a full section o f said lter. f

-8. In an electric system, a line, receiving terminals therefor, and m .ins for preventing undesired frequencies from belng'im;4 Vpressed onl said terminals while offering substantially equal attenuation .for frequen` cies within the transmission range, said` means comprising an electric filter -of .a

-plurality of'sirnilars sections, each comprising 'inductance and capacity and an electri-v cal network,said network comprising an inductance, and impedance in series with -inductance andacapacity vin shunt to said impedance having such electrical values that the equality .of transmission through said filter and network is improved thereby 9. In an .electric system, a line, receiving terminals therefor, and means for preventing undesired" frequencies from being impressed on said terminals 'while 'offering substantially .uniform impedance for frequencies'within the transmission range, said means comprising an electric filter and` an` electrical netwerk, said network comprising a resonant circuit and the rimary winding `of a transformer, said vwinding being' in series ,with said resonant circuit, the secondary of said transformer being associated with said receiving' terminals.

l0. In an electric system, a line, receivterminals therefor and means 'for preventing undesired lfrequencies from .being impressed on said terminals whileoffering substantially equal attenuation for frequencies within the transmission range, said' means comprisimr a filter and an electrical network, said filter comprisinga section having predetermined electrical characteristics and a second section having an electrical characteristic ,36 the value of the corresponding electrical value of said first section, said network comprising a resonant circuit and an impedance connected to saidI4 second section.y

1l. In an electric system, a line, means for amplifying currents from said, line,- means interposed between said line and said first means for reventing undesired frei quencies from being impressed on said first stantially equal attenuation for frequencies within the transmission rang'e, said means comprising a filter and a network, said networkcomprising a resonant circuit and a primary wind-4 ing of ai transformer, the secondary .of said transformer being associated with said first means.

means while ofi'fering su said .means comprising. a filter of finite lengthl and ai lumped network for simulating the `im edance of the remainder'of saidv filter of iii nite length and a vacuum tube repeater associated 'with/said network. 13. 2A. wave filter of a plurality of similar sections in combination with a network "siniulatinghe impedance of the corresponding infinite filter, said network comprising\an inductance, a resistance in series with said inductance, and a capacity' in shunt to said inductance.

14.7 In an electric system, a line, receiving terminalsl therefor, and means forpreventing undesired frequencies from being impressed on said terminals while offeringsub-v 'stantially av uniform impedance for frequencies within the transmission range, said vmeans comprising an electric filter' and an Aelectrical network, said network comprisingan impedance in series with said inductance and a said inductance. 'l f15. In combination, an electric wave filter o connected thereto, said network being connected to a section of said filter ha'ving an `electrical characteristic of a value a proximately eight-tenths the value of sai characteristic'in another section of said filter, and being so roportioned with res ect to the filter that t 1e impedance of the fi ter for all frequencies within the transmission range is substantially uniform. 16. A line, a filter therefor' comprising inductance elements in series with the line, capacity elements in shunt to the line, and a network for maintaining the attenuationfof all frequencies within the transmission range of said filter substantially equal, said network com rising a resonant circuit and a resistance e ectively in series with the iine.- 17 In combination, a transmission line, a lumped electrical network for said line cornprisin'g aflurality of similarrecurring sections, sai network having a nonaxniform impedance for a certain range of impressed frequencies and a second network associated with said first network for making more yuniform the impedance transmission through said first network, said second network comprising a parallel resonant circuit eHectively .in series with a substantially pure resistance. In witness my name this 11th day of Jul 'A. D., 1919.

EDWARD O. CRIVEN.

\a plurality of Asections and a network4 whereof, I hereunto-subscribe 

